using System;
using System.Runtime;
using System.Runtime.InteropServices;

namespace PickGold.Zlib
{

	/// <summary>
	/// Describes how to flush the current deflate operation.
	/// </summary>
	/// <remarks>
	/// The different FlushType values are useful when using a Deflate in a streaming application.
	/// </remarks>
	public enum FlushType
	{
		/// <summary>No flush at all.</summary>
		None = 0,

		/// <summary>Closes the current block, but doesn't flush it to
		/// the output. Used internally only in hypothetical
		/// scenarios.  This was supposed to be removed by Zlib, but it is
		/// still in use in some edge cases.
		/// </summary>
		Partial,

		/// <summary>
		/// Use this during compression to specify that all pending output should be
		/// flushed to the output buffer and the output should be aligned on a byte
		/// boundary.  You might use this in a streaming communication scenario, so that
		/// the decompressor can get all input data available so far.  When using this
		/// with a ZlibCodec, <c>AvailableBytesIn</c> will be zero after the call if
		/// enough output space has been provided before the call.  Flushing will
		/// degrade compression and so it should be used only when necessary.
		/// </summary>
		Sync,

		/// <summary>
		/// Use this during compression to specify that all output should be flushed, as
		/// with <c>FlushType.Sync</c>, but also, the compression state should be reset
		/// so that decompression can restart from this point if previous compressed
		/// data has been damaged or if random access is desired.  Using
		/// <c>FlushType.Full</c> too often can significantly degrade the compression.
		/// </summary>
		Full,

		/// <summary>Signals the end of the compression/decompression stream.</summary>
		Finish,
	}


	/// <summary>
	/// The compression level to be used when using a DeflateStream or ZlibStream with CompressionMode.Compress.
	/// </summary>
	public enum CompressionLevel
	{
		/// <summary>
		/// None means that the data will be simply stored, with no change at all.
		/// If you are producing ZIPs for use on Mac OSX, be aware that archives produced with CompressionLevel.None
		/// cannot be opened with the default zip reader. Use a different CompressionLevel.
		/// </summary>
		None = 0,
		/// <summary>
		/// Same as None.
		/// </summary>
		Level0 = 0,

		/// <summary>
		/// The fastest but least effective compression.
		/// </summary>
		BestSpeed = 1,

		/// <summary>
		/// A synonym for BestSpeed.
		/// </summary>
		Level1 = 1,

		/// <summary>
		/// A little slower, but better, than level 1.
		/// </summary>
		Level2 = 2,

		/// <summary>
		/// A little slower, but better, than level 2.
		/// </summary>
		Level3 = 3,

		/// <summary>
		/// A little slower, but better, than level 3.
		/// </summary>
		Level4 = 4,

		/// <summary>
		/// A little slower than level 4, but with better compression.
		/// </summary>
		Level5 = 5,

		/// <summary>
		/// The default compression level, with a good balance of speed and compression efficiency.
		/// </summary>
		Default = 6,
		/// <summary>
		/// A synonym for Default.
		/// </summary>
		Level6 = 6,

		/// <summary>
		/// Pretty good compression!
		/// </summary>
		Level7 = 7,

		/// <summary>
		///  Better compression than Level7!
		/// </summary>
		Level8 = 8,

		/// <summary>
		/// The "best" compression, where best means greatest reduction in size of the input data stream.
		/// This is also the slowest compression.
		/// </summary>
		BestCompression = 9,

		/// <summary>
		/// A synonym for BestCompression.
		/// </summary>
		Level9 = 9,
	}

	/// <summary>
	/// Describes options for how the compression algorithm is executed.  Different strategies
	/// work better on different sorts of data.  The strategy parameter can affect the compression
	/// ratio and the speed of compression but not the correctness of the compresssion.
	/// </summary>
	public enum CompressionStrategy
	{
		/// <summary>
		/// The default strategy is probably the best for normal data.
		/// </summary>
		Default = 0,

		/// <summary>
		/// The <c>Filtered</c> strategy is intended to be used most effectively with data produced by a
		/// filter or predictor.  By this definition, filtered data consists mostly of small
		/// values with a somewhat random distribution.  In this case, the compression algorithm
		/// is tuned to compress them better.  The effect of <c>Filtered</c> is to force more Huffman
		/// coding and less string matching; it is a half-step between <c>Default</c> and <c>HuffmanOnly</c>.
		/// </summary>
		Filtered = 1,

		/// <summary>
		/// Using <c>HuffmanOnly</c> will force the compressor to do Huffman encoding only, with no
		/// string matching.
		/// </summary>
		HuffmanOnly = 2,
	}


	/// <summary>
	/// An enum to specify the direction of transcoding - whether to compress or decompress.
	/// </summary>
	public enum CompressionMode
	{
		/// <summary>
		/// Used to specify that the stream should compress the data.
		/// </summary>
		Compress = 0,
		/// <summary>
		/// Used to specify that the stream should decompress the data.
		/// </summary>
		Decompress = 1,
	}


	/// <summary>
	/// A general purpose exception class for exceptions in the Zlib library.
	/// </summary>
	[Guid("ebc25cf6-9120-4283-b972-0e5520d0000E")]
	public class ZlibException : Exception
	{
		/// <summary>
		/// The ZlibException class captures exception information generated
		/// by the Zlib library.
		/// </summary>
		public ZlibException()
			: base()
		{
		}

		/// <summary>
		/// This ctor collects a message attached to the exception.
		/// </summary>
		/// <param name="s">the message for the exception.</param>
		public ZlibException(System.String s)
			: base(s)
		{
		}
	}


	internal class SharedUtils
	{
		/// <summary>
		/// Performs an unsigned bitwise right shift with the specified number
		/// </summary>
		/// <param name="number">Number to operate on</param>
		/// <param name="bits">Ammount of bits to shift</param>
		/// <returns>The resulting number from the shift operation</returns>
		public static int URShift(int number, int bits)
		{
			return (int)((uint)number >> bits);
		}

#if NOT
        /// <summary>
        /// Performs an unsigned bitwise right shift with the specified number
        /// </summary>
        /// <param name="number">Number to operate on</param>
        /// <param name="bits">Ammount of bits to shift</param>
        /// <returns>The resulting number from the shift operation</returns>
        public static long URShift(long number, int bits)
        {
            return (long) ((UInt64)number >> bits);
        }
#endif

		/// <summary>
		///   Reads a number of characters from the current source TextReader and writes
		///   the data to the target array at the specified index.
		/// </summary>
		///
		/// <param name="sourceTextReader">The source TextReader to read from</param>
		/// <param name="target">Contains the array of characteres read from the source TextReader.</param>
		/// <param name="start">The starting index of the target array.</param>
		/// <param name="count">The maximum number of characters to read from the source TextReader.</param>
		///
		/// <returns>
		///   The number of characters read. The number will be less than or equal to
		///   count depending on the data available in the source TextReader. Returns -1
		///   if the end of the stream is reached.
		/// </returns>
		public static System.Int32 ReadInput(System.IO.TextReader sourceTextReader, byte[] target, int start, int count)
		{
			// Returns 0 bytes if not enough space in target
			if (target.Length == 0) return 0;

			char[] charArray = new char[target.Length];
			int bytesRead = sourceTextReader.Read(charArray, start, count);

			// Returns -1 if EOF
			if (bytesRead == 0) return -1;

			for (int index = start; index < start + bytesRead; index++)
				target[index] = (byte)charArray[index];

			return bytesRead;
		}


		internal static byte[] ToByteArray(System.String sourceString)
		{
			return System.Text.UTF8Encoding.UTF8.GetBytes(sourceString);
		}


		internal static char[] ToCharArray(byte[] byteArray)
		{
			return System.Text.UTF8Encoding.UTF8.GetChars(byteArray);
		}
	}

	internal static class InternalConstants
	{
		internal static readonly int MAX_BITS = 15;
		internal static readonly int BL_CODES = 19;
		internal static readonly int D_CODES = 30;
		internal static readonly int LITERALS = 256;
		internal static readonly int LENGTH_CODES = 29;
		internal static readonly int L_CODES = (LITERALS + 1 + LENGTH_CODES);

		// Bit length codes must not exceed MAX_BL_BITS bits
		internal static readonly int MAX_BL_BITS = 7;

		// repeat previous bit length 3-6 times (2 bits of repeat count)
		internal static readonly int REP_3_6 = 16;

		// repeat a zero length 3-10 times  (3 bits of repeat count)
		internal static readonly int REPZ_3_10 = 17;

		// repeat a zero length 11-138 times  (7 bits of repeat count)
		internal static readonly int REPZ_11_138 = 18;

	}

	internal sealed class StaticTree
	{
		internal static readonly short[] lengthAndLiteralsTreeCodes = new short[] {
            12, 8, 140, 8, 76, 8, 204, 8, 44, 8, 172, 8, 108, 8, 236, 8,
            28, 8, 156, 8, 92, 8, 220, 8, 60, 8, 188, 8, 124, 8, 252, 8,
             2, 8, 130, 8, 66, 8, 194, 8, 34, 8, 162, 8, 98, 8, 226, 8,
            18, 8, 146, 8, 82, 8, 210, 8, 50, 8, 178, 8, 114, 8, 242, 8,
            10, 8, 138, 8, 74, 8, 202, 8, 42, 8, 170, 8, 106, 8, 234, 8,
            26, 8, 154, 8, 90, 8, 218, 8, 58, 8, 186, 8, 122, 8, 250, 8,
             6, 8, 134, 8, 70, 8, 198, 8, 38, 8, 166, 8, 102, 8, 230, 8,
            22, 8, 150, 8, 86, 8, 214, 8, 54, 8, 182, 8, 118, 8, 246, 8,
            14, 8, 142, 8, 78, 8, 206, 8, 46, 8, 174, 8, 110, 8, 238, 8,
            30, 8, 158, 8, 94, 8, 222, 8, 62, 8, 190, 8, 126, 8, 254, 8,
             1, 8, 129, 8, 65, 8, 193, 8, 33, 8, 161, 8, 97, 8, 225, 8,
            17, 8, 145, 8, 81, 8, 209, 8, 49, 8, 177, 8, 113, 8, 241, 8,
             9, 8, 137, 8, 73, 8, 201, 8, 41, 8, 169, 8, 105, 8, 233, 8,
            25, 8, 153, 8, 89, 8, 217, 8, 57, 8, 185, 8, 121, 8, 249, 8,
             5, 8, 133, 8, 69, 8, 197, 8, 37, 8, 165, 8, 101, 8, 229, 8,
            21, 8, 149, 8, 85, 8, 213, 8, 53, 8, 181, 8, 117, 8, 245, 8,
            13, 8, 141, 8, 77, 8, 205, 8, 45, 8, 173, 8, 109, 8, 237, 8,
            29, 8, 157, 8, 93, 8, 221, 8, 61, 8, 189, 8, 125, 8, 253, 8,
            19, 9, 275, 9, 147, 9, 403, 9, 83, 9, 339, 9, 211, 9, 467, 9,
            51, 9, 307, 9, 179, 9, 435, 9, 115, 9, 371, 9, 243, 9, 499, 9,
            11, 9, 267, 9, 139, 9, 395, 9, 75, 9, 331, 9, 203, 9, 459, 9,
            43, 9, 299, 9, 171, 9, 427, 9, 107, 9, 363, 9, 235, 9, 491, 9,
            27, 9, 283, 9, 155, 9, 411, 9, 91, 9, 347, 9, 219, 9, 475, 9,
            59, 9, 315, 9, 187, 9, 443, 9, 123, 9, 379, 9, 251, 9, 507, 9,
             7, 9, 263, 9, 135, 9, 391, 9, 71, 9, 327, 9, 199, 9, 455, 9,
            39, 9, 295, 9, 167, 9, 423, 9, 103, 9, 359, 9, 231, 9, 487, 9,
            23, 9, 279, 9, 151, 9, 407, 9, 87, 9, 343, 9, 215, 9, 471, 9,
            55, 9, 311, 9, 183, 9, 439, 9, 119, 9, 375, 9, 247, 9, 503, 9,
            15, 9, 271, 9, 143, 9, 399, 9, 79, 9, 335, 9, 207, 9, 463, 9,
            47, 9, 303, 9, 175, 9, 431, 9, 111, 9, 367, 9, 239, 9, 495, 9,
            31, 9, 287, 9, 159, 9, 415, 9, 95, 9, 351, 9, 223, 9, 479, 9,
            63, 9, 319, 9, 191, 9, 447, 9, 127, 9, 383, 9, 255, 9, 511, 9,
             0, 7, 64, 7, 32, 7, 96, 7, 16, 7, 80, 7, 48, 7, 112, 7,
             8, 7, 72, 7, 40, 7, 104, 7, 24, 7, 88, 7, 56, 7, 120, 7,
             4, 7, 68, 7, 36, 7, 100, 7, 20, 7, 84, 7, 52, 7, 116, 7,
             3, 8, 131, 8, 67, 8, 195, 8, 35, 8, 163, 8, 99, 8, 227, 8
        };

		internal static readonly short[] distTreeCodes = new short[] {
            0, 5, 16, 5, 8, 5, 24, 5, 4, 5, 20, 5, 12, 5, 28, 5,
            2, 5, 18, 5, 10, 5, 26, 5, 6, 5, 22, 5, 14, 5, 30, 5,
            1, 5, 17, 5, 9, 5, 25, 5, 5, 5, 21, 5, 13, 5, 29, 5,
            3, 5, 19, 5, 11, 5, 27, 5, 7, 5, 23, 5 };

		internal static readonly StaticTree Literals;
		internal static readonly StaticTree Distances;
		internal static readonly StaticTree BitLengths;

		internal short[] treeCodes; // static tree or null
		internal int[] extraBits;   // extra bits for each code or null
		internal int extraBase;     // base index for extra_bits
		internal int elems;         // max number of elements in the tree
		internal int maxLength;     // max bit length for the codes

		private StaticTree(short[] treeCodes, int[] extraBits, int extraBase, int elems, int maxLength)
		{
			this.treeCodes = treeCodes;
			this.extraBits = extraBits;
			this.extraBase = extraBase;
			this.elems = elems;
			this.maxLength = maxLength;
		}
		static StaticTree()
		{
			Literals = new StaticTree(lengthAndLiteralsTreeCodes, Tree.ExtraLengthBits, InternalConstants.LITERALS + 1, InternalConstants.L_CODES, InternalConstants.MAX_BITS);
			Distances = new StaticTree(distTreeCodes, Tree.ExtraDistanceBits, 0, InternalConstants.D_CODES, InternalConstants.MAX_BITS);
			BitLengths = new StaticTree(null, Tree.extra_blbits, 0, InternalConstants.BL_CODES, InternalConstants.MAX_BL_BITS);
		}
	}



	/// <summary>
	/// Computes an Adler-32 checksum.
	/// </summary>
	/// <remarks>
	/// The Adler checksum is similar to a CRC checksum, but faster to compute, though less
	/// reliable.  It is used in producing RFC1950 compressed streams.  The Adler checksum
	/// is a required part of the "ZLIB" standard.  Applications will almost never need to
	/// use this class directly.
	/// </remarks>
	///
	/// <exclude/>
	public sealed class Adler
	{
		// largest prime smaller than 65536
		private static readonly uint BASE = 65521;
		// NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1
		private static readonly int NMAX = 5552;


#pragma warning disable 3001
#pragma warning disable 3002

		/// <summary>
		///   Calculates the Adler32 checksum.
		/// </summary>
		/// <remarks>
		///   <para>
		///     This is used within ZLIB.  You probably don't need to use this directly.
		///   </para>
		/// </remarks>
		/// <example>
		///    To compute an Adler32 checksum on a byte array:
		///  <code>
		///    var adler = Adler.Adler32(0, null, 0, 0);
		///    adler = Adler.Adler32(adler, buffer, index, length);
		///  </code>
		/// </example>
		public static uint Adler32(uint adler, byte[] buf, int index, int len)
		{
			if (buf == null)
				return 1;

			uint s1 = (uint)(adler & 0xffff);
			uint s2 = (uint)((adler >> 16) & 0xffff);

			while (len > 0)
			{
				int k = len < NMAX ? len : NMAX;
				len -= k;
				while (k >= 16)
				{
					//s1 += (buf[index++] & 0xff); s2 += s1;
					s1 += buf[index++]; s2 += s1;
					s1 += buf[index++]; s2 += s1;
					s1 += buf[index++]; s2 += s1;
					s1 += buf[index++]; s2 += s1;
					s1 += buf[index++]; s2 += s1;
					s1 += buf[index++]; s2 += s1;
					s1 += buf[index++]; s2 += s1;
					s1 += buf[index++]; s2 += s1;
					s1 += buf[index++]; s2 += s1;
					s1 += buf[index++]; s2 += s1;
					s1 += buf[index++]; s2 += s1;
					s1 += buf[index++]; s2 += s1;
					s1 += buf[index++]; s2 += s1;
					s1 += buf[index++]; s2 += s1;
					s1 += buf[index++]; s2 += s1;
					s1 += buf[index++]; s2 += s1;
					k -= 16;
				}
				if (k != 0)
				{
					do
					{
						s1 += buf[index++];
						s2 += s1;
					}
					while (--k != 0);
				}
				s1 %= BASE;
				s2 %= BASE;
			}
			return (uint)((s2 << 16) | s1);
		}
#pragma warning restore 3001
#pragma warning restore 3002

	}

}
